Collapsible wheelchair

ABSTRACT

This invention relates to a collapsible wheelchair (1) having a chassis (2) composed of two separate, lateral symmetrical sides (6) each including at least one virtually vertical upright bar (7), an upper arm (12), a lower arm (15) a carrying wheel (10) at the rear of the chassis and a guiding wheel (17) at the front of the chassis. The upper and lower arms (12, 15) are solid with the upright bar (7) and the lateral sides are only connected by the joint action of a seat (3) and a back (4), each including two rigid and symmetrical half-pieces (18, 28), articulated between each other following a median axis respectively of seat (3) and back (4).

This invention relates to a seat, chair or wheelchair that can be foldedfrom an unfolded position for use to a folded position when not in use.

Such wheelchairs are already known and they generally include a chassisequipped with two carrying wheels and two guiding wheels composed on onehand of two upright bars to which is connected a back, often of aflexible material and on the other hand of two lateral sides to which isconnected a seat generally made of canvas, and finally a set ofarticulated cross braces enabling the wheelchair to be folded bybringing its two sides together.

In this respect the French Patent FR-A-2.252.838 describes a wheelchairwith a rigid seat and back, the characteristic of which is to becollapsible; this particular wheelchair is composed of two symmetricalparts following a vertical axial plane joined together by twoarticulation sets, one at the rear of the back and the other under theseat. Such a wheelchair already has an important advantage overwheelchairs known to date, in as far as it offers a seat and a back of arigid material while enabling the unit to fold easily. But in spite ofthis, such a wheelchair has the drawback of being relatively heavy andexpensive due to the double articulation it includes and which increasesthe weight of the chair which, by nature, is intended to be transportedoften by the disabled person him/herself.

The collapsible wheelchair proposed according to this inventionsignificantly eliminates the above-mentioned drawbacks in that iteliminates any cross brace from the articulation allowing the unfoldingof the rigid seat and rigid back of a collapsible wheelchair. In thisrespect, according to the invention, the collapsible wheelchair which isequipped with a chassis composed of two separate identical lateral sideseach including one virtually vertical upright bar, a lower arm bearing acarrying wheel at the rear and a guiding wheel at the front, and ahigher arm--the said higher and lower arms being solid with thevirtually vertical upright bar, is characterized in that the lateralsides are only joined together by the joint action of a seat, a back anda foot rest including one or two parts articulated between each other,the seat and the back both being composed of two symmetrical, rigidhalf-pieces articulated between each other along the median axisrespectively of the seat and the back.

According to a preferred mode of the invention, the two half-pieces ofthe seat and the back are rigid parts of a virtually general rectangularshape forming respectively both the seat and the back, with arectangular cross-section and a second central part with a virtuallytriangular cross-section offering an upper side, a lateral sideperpendicular to the upper side and a lower sloped side, the externalwing including on its external edge a tubular arrangement acting as ahinge to associate in rotation the seat or the back with the chassis,the central part of the half-pieces being substantially, although notexclusively, equipped with tubular eyelets placed along the intersectionbetween the lateral side and the lower side, to form the central hingebetween the two half-pieces of the seat or back.

Such a collapsible wheelchair is very easy to fold since, in lifting thecentral hinge between the two half-pieces of the seat, the two lateralsides of the chair come together and cause the central hinge to foldbetween the two half-pieces of the back. The wheelchair is thuscompletely folded and by a reverse operation, just as easy, it isunfolded and ready to use.

According to a first variant each lateral side of the chassis can beformed by a generally quadrangular shaped frame, a first side of whichcorresponds to the seat, a second side extended upwards corresponds tothe back and a third side extended downwards and curved towards thefront correspond to the foot rest ; the carrying wheel is mounted closeto the lower top of the back side and the guiding wheel, under thefourth side which is preferably parallel to the seat side. This chassiscan be made of a tubular metal structure for example.

According to a second variant, each lateral side of the chassis ismainly composed of an elbowed side bar offering a rising part on whichis articulated the back and a low part located under the seat, thecarrying wheel being mounted on the side bar in its elbowed part, theguiding wheel under the side bar in its low part and the foot rest on ashort arm solid with the front part of the side bar; another arm comingfrom the rising part of the side bar juts out from a point on the risingpart of the side bar located approximately in the lower third of thispart. The assembly of the side bar and seat and foot rest arms can, forexample, be made of folded sheet metal, in profiles or tubularstructure, screwed or welded.

Thus built, the wheelchair according to this invention offers theadvantage of providing remarkable comfort for the user due to thespecial rigidity of its seat which also procures the general suspensionof the wheelchair thanks to a certain reversible elasticity resultingfrom the chair design in two rigid half-pieces and simultaneously fromthe elimination of any triangulation of the chassis which, as known,does not permit any elastic deformation.

In addition, it is attractive and its easy collapsible system allows anyimaginable form of chassis.

Finally, it is very light and any kind of upholstery can be adapted toits rigid parts.

As a non limitative example, hereunder will be described variouselements of this invention with reference to the attached drawings inwhich:

FIG. 1 is a front view of the wheelchair according to the first variantof the invention in its folded position, not in use,

FIG. 2 is a partially exploded side view of the back of this samewheelchair, also in folded position, not in use,

FIG. 3 is a side view, on a larger scale, of the seat of the wheelchairin its unfolded position.

FIG. 4 is a side view of the seat according to FIG. 3 in its foldedposition, not in use,

FIG. 5 is a side view similar to FIG. 3, according to another embodimentof the seat of the wheelchair according to this invention.

FIG. 6 is a side view of the folded seat of the wheelchair according toFIG. 5.

FIG. 7 is an underneath view, on a larger scale, of the embodiment shownin FIGS. 5 and 6, the seat of the wheelchair being unfolded,

FIG. 8 is a general view of the seat of FIG. 7, folded,

FIG. 9 is a cutaway view, following line I--I' of FIG. 1, of theextended hinge of the wheelchair,

FIG. 10 is a perspective view, on a larger scale, of the half-pieceforming the seat and the back of the wheelchair according to theinvention,

FIG. 11 is a general side view of the second variant of the wheelchairaccording to the invention in its unfolded position.

According to a first variant, this invention concerns a collapsiblewheelchair 1, according to the FIGS. 1 and 2, composed of a chassis 2including a real seat 3, located, when in its unfolded position, in ahorizontal plane, of a back 4 in a virtually vertical plane and of afoot rest 5 also in a virtually horizontal plane, at a lower level thanthat of the seat 3.

According to the invention, the chassis 2 is composed of 2 lateralsymmetrical sides 6, totally separated from each other, which allowstheir mass production. These 2 lateral sides 6 are mounted in planesparallel to each other and perpendicular to the virtually horizontalplane of the seat 3 and of the foot rest 5, as well as to the verticalplane of the back 4, the said back 4, seat 3 and foot rest 5 forming theessential connecting elements of the lateral sides 6 of the chassis 2.

Each lateral side 6, according to a preferred (but non limitative)embodiment of the wheelchair 1 of the invention, a virtually verticalupright bar 7, carrying at the end of its top part a handle 8,horizontal or slightly sloped, in relation to the horizontal, towardsthe front of the wheelchair 1, so that a person accompanying thewheelchair's user has a good grip.

The vertical upright bar 7 carries at its far lower part, opposite theend carrying the handle 8, a bearing 9, carrying a wheel 10 with a largediameter, bearing down on the ground. This wheel 10 is doubled inparallel by a drive wheel 10a solid with the carrying wheel 10 of thewheelchair 1.

Each lateral side 6 of the chassis 2 then includes a tubular element 11in the shape of an "S", the upper end of which is rigidly solid with theupright bar 7 and the upper horizontal arm 12 of which serves as supportto the seat 3 such as detailed thereafter.

The central part 13 of the "S" shaped element 11 is directed downwards,slightly sloped forward and connected to a short arm 14, virtuallyhorizontal or slightly sloped downwards and receiving the foot rest 5.The central part 13 of the "S" element 11 is equipped with a horizontalcrossbar 15 joining the vertical bar 7.

The crossbar 15 bears a fork 16 carrying a front guiding wheel 17orientable around a vertical axis. This front wheel 17 is of a muchsmaller diameter that the carrying wheel 10. It is obvious that the fork16 can be moved along the crossbar 15 as far as required.

It results from the previous description that the lateral sides 6 of thewheelchair, before assembly, are totally separate one from the other.

According to the invention, the seat 3 of the wheelchair 1 on one handand the back 4 on the other hand are of a virtually identical design,the sole difference of which resides in the smaller length of the back 4compared with the seat 3, in the vertical direction for the back 4 andhorizontal for the seat 3, parallel to the two lateral sides 6 of thechair 1.

According to the invention, the seat 3 is composed of two rigidhalf-pieces 18, rectangular in shape, symmetrical, one on the right, theother on the left of the seat 3. Each half-piece 18 is composed of afirst part forming the external wing 19 of the seat and a second centralpart 20, making an obtuse angle between them, slightly smaller than180°.

The transverse cross-section of the external wing 19 of the half-pieces18 is rectangular, while the transversal section of the central part 20is triangular, offering a flat upper surface 21, and extreme surface 22perpendicular to the upper surface 21 and a lower, sloped, surface 25.

The upper surface 23 of the external wing 19 is slightly sloped inrelation to the upper surface 21 of the central part 20, of a same valueof angle as between the two parts 19, 20 of the seat 3.

In addition, the external wing includes on its free external edge atubular arrangement 24a which enables it to slide onto the upper arm 12of the "S" element 11 used as support to the seat 3.

In a first embodiment of the chair 1 according to the inventionincluding a seat 3 and a back 4 obtained by plastic injection, thecentral part 20 is equipped at the intersection of the extreme surface22 and the inside surface 25, with a series of tubular eyelets 26 withthe same inner diameter alternating between the two coaxial right andleft half-pieces 18 of the seat 3 fitting onto a same core to form acentral hinge 27, associating the two half-pieces 18 of the seat 3 in atipping position between each other; in this way, the central hinge 27,placed at the intersection of the lower surfaces 25 of the twohalf-pieces 18 only allows an upward rotation of the half-pieces 18 suchas shown by the arrows f1, bringing the seat 3 from folded station(FIGS. 4 and 6) to an unfolded station (FIGS. 3 and 5). During thisupward rotary movement of the two half-pieces 18, the tubulararrangements 24a of the outside wings 19 of the half-pieces 18, rotateround the upper arm 12 of the "S" element 11, to form an external hinge24 between the seat 3 and the lateral side 6 of the chassis 2.

In a lowered position of the seat 3 shown in FIGS. 3 and 5, the twoupper sides 21 of the central parts 20 of the two half-pieces 18 arecoplanar and horizontal. The two upper sides 23 of the two externalwings 19 of the two half-pieces 18 being slightly directed upwards, theseat 3 offers a curve that can be upholstered to improve the seatingconditions of the user.

In this position, the tubular arrangements 24a, associated with theupper arms 12 of the "S" element 11 of each of the two lateral sides 6of the chassis 2 are in their relative position the furthest apart andthe wheelchair 1 is ready for use. It can be noted that in thissituation, the two half-pieces 18 being in contact by their far surfaces22 give the stability to the seat and consequently the rigidity andstability of the wheelchair.

In addition, when the two half-pieces 18 of the seat 3 are lifted tofold the seat 3 and with it the wheelchair 1 as it has been mentioned,the back 4 follows a similar collapsible movement towards the front ofthe chair 1 and on the contrary, when the seat 3 is unfolded bringingthe far surfaces 22 of the half-pieces 18 of the seat 3 one against eachother, the two half pieces 28 of the back 4 unfold in the same way byrotation round the central hinge 27 connecting them; the far surfaces 32of the half-edges 28 stretching out in length parallel to the twoupright bars 7 of the chassis 2 also come together to form the back 4,composed as a seat 3 by a central part 30 and an external wing 29equipped on its edges with hinges 34 allowing a rotation round avertical upright bar 7 of the chassis 2.

According to a second form of execution of the proposed invention, theseat 3 and the back 4 are made of carbon fibre or glass fibre. Thesematerials are highly resistant and in particular very light, which is adecisive argument for the production of a wheelchair 1 according to theinvention. On the other hand, due to the difficulty of machining suchmaterials, it is not easy to obtain a bore hole to receive the axisforming the rotation hinge between the mobile parts.

According to the invention, and in reference to FIG. 9, thearticulations of parts 18, 28 in rotation on the tubular structures 12and 7 of the chassis 2 are obtained by means of a set of rings 35,preferably made of a synthetic material, positioned by precise sliding,in the right place on the tubular structure of the chassis 2, whether itis the upright bar 7 for the back 4 or the arm 12 for the seat 3. Theserings 35 are mounted at the two ends of the tubular parts 24a of thehinges 24, 34 of the seat 3 and of the back 4, previously fitted ontothe structural elements 12, 7 so that the said hinges 24, 34 can rotatefreely, Without play, on the rings 35 which are also equipped with acircular shoulder 36 to obtain on one hand an axial stop for the tubularends 24a of the hinges 24, 34 and on the other hand a sufficient bearingarea for the solidarization of the said rings 35 on the structuralelements 12, 7 of the chassis 2. As a complement, inside this structure12, 7 and perpendicular to each articulation formed by the hinges 24, 34we have a core 37, preferably made of cylindrical shaped metal and witha diameter such that it penetrates easily into the inside of thestructure 12, 7. This core 37 includes, radially, a threaded hole 38which is positioned perpendicular to drilled hole 39 made for thispurpose in the fixed structure 12, 7 and a drilled hole 42 also providedin the shoulder 36 of the rings 35. A screw 40 crosses these holes 39,42 and screws into the threading of the threaded hole 38 of the core 37to make solid each ring 35 with the fixed structure 12, 7; in this way,the hinges 24, 34 are in rotation without any clearance on the rings 35thus substantially providing the axial stop device of the seat 3 and ofthe back 4 mounted on the chassis 2 of the wheelchair 1. It can be notedthat the assembly that has just been described is particularlyinteresting as it avoids the ovalization of the rotation guides which isgenerally responsible for the difficulties of rotation between parts,creating a disagreeable inconvenience for the user of the wheelchairaccording to the invention.

For the same reasons resulting from the difficulties of machiningcomposite materials, it has been decided, in this embodiment of thewheelchair 1 according to the invention, to replace the central hinges27 between the half- pieces 18 of the seat 3 and 28 of the back 4 bystraps stuck alternatively onto the two lower sides 25 and the two farsides 22, 32 of the two joining half-pieces 18,28. In this way, we shallalternatively use (FIGS. 7 and 8) a strap 41 stuck to the two lowersides 25, followed by a strap 42 partly stuck on the lower side 25 ofthe left half-piece 18, 28 and partly on the far side 22, 32 of theright half-piece 18, 28, then a strap 43 partly stuck on the lower side25 of the left half-piece 18, 28, opposite each other, so as to form, byrepeating as often as needs be, the alteration of the straps 41, 42, 43,the seat 3 or the back 4.

Under these conditions of realization, the half-pieces 18, 28 will besubstantially equipped with means of centering when they are in anunfolded position of use; in this respect, and according to FIG. 10,each far side 22 or 32 of the two half-pieces 18 or 28 respectivelyforming the seat 3 and the back 4 is equipped on one side, for exampleon the left, with a point 44 and on the right with a crater 45 whosehollow shape matches the point 44 so that when the wheelchair isunfolded the half-pieces 18, 25 come, into contact by their far side 22,32 opposite each other, point 44 fitting into the crater 45 of the otherand reciprocally.

According to another characteristic of the invention, the foot rest 5 ofthe wheelchair 1 according to the invention, is composed of a plate orboard 46 (FIG. 1) in one piece over the whole width of the wheelchair,fitted to one of the short arms 14 of one of the lateral sides 6 of thechassis 2 by hinges 47 which allow it to tip upwards from a horizontalposition of use to a vertical rest position. In the position of use, thefoot rest 5 fits by an elongated hook 48 onto the other short arm 14 ofthe chassis 2. This elongated hook 48 preferably clips onto the saidshort arm 14 onto which it comes to rest when the wheelchair is in itsunfolded position of use.

In the folded position of the wheelchair 1 the foot rest 5 tips upwardswhilst in its unfolded position of use the foot rest 5, connected to oneof the short arms 14 of the chassis 2 by the hinges 47 and to the othershort arm 14 by clipping the elongated hook 48 serves as an extra meansof spacing between the lateral sides 6 forming the chassis 2 of thewheelchair 1.

The foot rest can be formed of two articulated half elements on thelower front parts 14 of the two lateral sides 6. These two half elementscan either be articulated between each other like seat and back or bemade separate and preferably attachable by any suitable device when theyare in the position of use.

In addition, the seat such as it is shown in FIGS. 1 and 2 is designedlike a chair which facilitates the access to the drive wheels 10a.However, if the user must be firmly held onto the seat, means of holdingor attaching can be provided such as arm rests that can be folded inrest position along the upright bars 7.

It is obvious that a seat such as that shown in FIGS. 1 and 2 is easy touse and facilitates the approach to a bed, a table, a toilet seat, awashbasin, a car and the transfer from the wheelchair to a classicalseat or bed or in and out of a car.

In reference to FIG. 11, we will describe a second variant of thewheelchair according to the invention. The elements identical to thoseof the previous figures or equivalent have the same reference numbers.In FIG. 11, seat 3, back 4 and foot rest 5, are unfolded. The seat ismainly composed of two sides 6 as in the previous examples, two carryingwheels (and their drive wheel 10a) and two guiding wheels 17.

The sides 6 are connected by the seat 3, the back 4 and the foot rest 5which can be realized as described above.

The seat 3 is articulated at 24 on the lateral sides 6 and the back 4 at34. The seat 3 is articulated on the lateral sides 6 at 24 and on theback 4 at 34.

Each side 6 is mainly formed by an elbowed side bar composed of avirtually vertical upright bar 7 corresponding to the back 4 and of alower arm 15, virtually horizontal, on the end of which is mounted thefoot rest 5 on a short arm 14, itself elbowed to carry the foot rest 5near the ground. The carrying wheel 10 is mounted at 9 near the elbow ofthe side bar formed by the arm 15 and the vertical upright bar 7, andthe guiding wheel 17 under the arms 15 towards the front at 16 close tothe foot rest 5 and its support 14.

The carrying wheel 10 and its coaxial drive wheel 10a are mounted on abearing solid with the side bar.

An arm 12 sticking out perpendicularly from the vertical upright bar 7of the side bar at an anchoring point located approximately within thelower third of the said upright bar 7 stretches horizontally towards thefront of the wheelchair 1 within the plane of each lateral side 6 tosupport the seat 3.

As in the first variant, the seat 3 is articulated at 24 on the upperarm 12 in an overhanging position and the back 4 on the upright bar 7 at34.

According to a preferred execution of the invention, the assembly of thesides 6 formed by the upright bar 7 and the arms 12 and 15 can be madeof welded folded sheet metal, of welded screwed profiles or of mountedlight alloy. In any case, the cross-section of the various parts 7, 12,15 composing the sides 6 can be rectangular or opened in a V or M shape.Each part can be a constant or variable section depending on themechanical stresses and in particular on the bending stresses mainly dueto the load and to the tensile strength due especially t the reaction ofthe ground which can be very irregular.

Thus the articulations 24, 34 may only concern a part of the section ofthe support element (respectively 3 and 6) as shown in FIG. 11.

It can be noted that the lower arm 15 plunges preferably downwards andforwards to clear the space under the seat 3 inasfar as possible and tofacilitate the approach movements of the user.

Handles 8 are provided as in the previous examples.

The guiding wheels 17 can be mounted classically according to theinvention. It is better for them to be of a small diameter to facilitatemovements. However, we are limited by the bumps in the ground which arenot compatible with wheels of too small a diameter.

The arm 14 of the foot rest 5 can be fixed to the lateral side 6. It ispossible for it to be removed, for example by sliding onto or into thearms 15, to fold upwards (which is an advantage for users with shortlegs) or to be adjustable in height.

It can also be noted that the lateral sides 6, the seat 3, the back 4,the foot rest 5 and a large part of the wheels 10, 10a and 17 can berealized in reinforced plastic, for example carbon or glass-fiber,giving a transparency to X-rays, which is a particular advantageespecially in hospital where it will allow a patient to remain in thewheelchair to undergo certain examinations, such as X-rays for example.

It can also be noted that if the supports 14 of the foot rest 5 areremovable, and therefore interchangeable at the end of the lower arm 15,a number of accessories can be mounted and removed at the end of theupper arms 12 (ashtray, tray, supports, cameras, etc.), the arm endsbeing shaped suitably.

I claim:
 1. A collapsible wheelchair (1), comprising:a chassis (2) formed of two identical separate individual lateral sides (6) each including at least one virtually vertical upright bar (7), an upper arm (12) and a lower arm (15), said upright bar (7) carrying a carrying wheel (10) at the back of said chassis (2) and a guiding wheel (17) at the front of said chassis; said upper and said lower arms (12, 15) being fixed to said upright bar (7); a seat (3) a back (4) and a foot rest (5); said seat (3) including two rigid symmetrical half-pieces (18) articulated between each other and connecting said two separate lateral sides together in a horizontal direction according to a median axis of said seat between said upper horizontal arms (12); said foot rest (5) being connected at one end thereof to one of said lateral sides; said back (4) including two rigid half-pieces (28) articulated between each other and connecting said two virtually vertical uprights bars (7) of separate lateral sides (6) together in a vertical direction according to a median axis of said back between said vertical uprights bars (7); and each of said two half-pieces (18, 28) forming said seat (3) and said back (4) including a first part having a rectangular transverse cross-section forming at least one of an outside external wing (19, 29) of at least one of said seat (3) and said back (4) and a second central part (20, 30) having a virtually triangular transverse cross-section offering an upper side (21) and a lateral side (22, 32) perpendicular to said upper side (21) and a lower sloped surface (25); said outside external wing (19, 29) including on its external edge a tubular arrangement (24a) acting as hinge (24, 34) for associating in rotation said at least one of said seat (3) and said back (4) respectively to said upper arm (12) and upright bar (7), the median part (20, 30) being provided with a central hinge (27) stretching along the intersection between said lateral side (22, 32) and a lower side (25) in such a way that when the wheelchair (1) is in its unfolded position of use, the two half-pieces (18, 28) come against each other by their lateral sides (22, 32) and when the armchair (1) is in its folded position, said lateral sides (22, 32) are in the same plane.
 2. The wheelchair (1) according to claim 1 wherein the upper side (23) of the outside wing (19, 29) of each half-piece (18, 28) offers a slight slope in relation to the upper side (21) of the central part (20, 30) of the said half-pieces (18, 28) so that when the wheelchair (1) is unfolded the two half-pieces (18, 28) form a curved seat giving a suspension effect and comfort to the user.
 3. The wheelchair (1) according to claim 1, wherein the articulation of the seat (3) and the back (4) respectively on the upper arm (12) of the lateral side (6) and on the upright bar (7) of the chassis (2) is formed by two rings (35) mounted at both ends of the hinges (24, 34) so that the tubular arrangement (24a) can freely and without clearance rotate on the said rings (35), the said rings fitting snuggly onto the fixed tubular structure (12, 7) of the wheelchair (1) inside of which is a hub (37) radially drilled by a threaded hole (38) perpendicular to a drilled hole (39) in the fixed structure (12, 7) of the chassis (2) and of a drilled hole (42) radially made in a shoulder (36) of the rings (35) into which is screwed a screw (40) which makes the rings (35) solid with the fixed structures (12, 7) of the chassis (2).
 4. The wheelchair (1) according to claim 1, wherein the central hinge (27) between the two mobile parts (18, 28) is realized by means of straps arranged alternatively so that to one strap (41) stuck on the two lower sides (25) of the half-pieces (18, 28) succeeds a strap (42) stuck partly to the lower side (25) of the left half-piece (18, 28) and partly on the lateral side (22, 32) of the right half-piece (18, 28) and a strap (43) partly stuck on the lower side (25) of the right half-piece (18, 28) and partly on the lateral side (22, 32) of the left half-piece (18, 28), this sequence being repeated as many times as necessary over the whole length of at least one of the seat (3) and said back (4).
 5. The wheelchair (1) according to claim 1 wherein characterized in that each lateral side (22, 32) of the half-pieces (18, 28) is provide don one side, for example on the left, with a point (44) and on the right with a crater (15), the hollow form of which matches the point (44) so that when the wheelchair is unfolded the half-pieces (18, 28) are in contact by their lateral sides (22, 32), opposite each other, the point (44) of one fitting into the crater (45) of the other and reciprocally.
 6. The wheelchair according to claim 1, wherein each said lateral side (6) comprising said vertical upright bar (7) and said lower horizontal arm (15) together form an elbowed side bar bearing said upper arm (12) which sticks out perpendicularly from said upright bar (7) at an anchoring point located approximately within a lower third of said upright bar (7) and stretches horizontally towards the front of the wheelchair (1) within the plane of each lateral side (6) to bear the seat.
 7. The wheelchair according to claim 1, wherein the ends of said upper arms (12) are shaped to receive accessories.
 8. A collapsible wheelchair (1), comprising:a chassis (2) formed of two identical separate lateral sides (6) each including at least one virtually vertical upright bar (7), and a lower arm (15) solid with said bar (7), and said chassis bearing a carrying wheel (10) at the back thereof and a guiding wheel (17) at the front thereof; an upper arm (12) solid with said upright bar (7); a seat (3), and a back (4) each including at least one piece connecting said lateral sides (6); said seat (3) and said back (4) each being formed of two rigid, symmetrical half-pieces (18, 28) articulated between each other according to the median axis of the seat (3) and the back (4), respectively; said lateral side (6) formed by said virtually upright bar (7) and said lower horizontal arm (15) together forming an elbowed side bar bearing said upper arm (12); said upper arm sticking out perpendicularly from said upright bar (7) at an anchoring point located approximately within the lower third thereof and stretching horizontally towards the front of said wheelchair (1) within the plane of each said lateral side (6) to bear said seat (3); each of said two half-pieces (18, 28) forming said seat (3) and said back (4) being formed of a first part with a rectangular transverse cross-section forming at least one of said outside wing (19, 29) of said seat (3) and a second central part (20, 30) with a virtually triangular transverse cross-section offering an upper surface (21) and a lateral side (22, 32) perpendicular to said upper surface (21) and a lower sloped side (25), said outside wing (19, 29) including on its external edge a tubular arrangement (24a) acting as hinge (24, 34) for associating in rotation said seat (3) to said upper arm (12) and said upright bar (7), the median part (20, 30) being equipped with a central hinge (27) stretching along the intersection between said lateral side (22, 32) and said lower side (25) in such a way that when said wheelchair (1) is in its unfolded position of use, said two half-pieces (18, 28) come against each other by their lateral sides (22, 32) and when the armchair (1) is in its folded position, said lateral sides (22, 32) are in the same plane. 